Methods and systems for saliva management with an oral device

The present application claims the benefit of provisional U.S. Application No. 60/987,707 (Attorney Docket No. 027094-000100US), filed Nov. 13, 2007, the full disclosure of which is incorporated herein by reference. This application is related to commonly-assigned U.S. application Ser. No. ______ (Attorney Docket No. 027094-000110US) and U.S. application Ser. No. ______ (Attorney Docket No. 027094-000120US), both filed on the same day as the present application and both of which are incorporated herein by reference.

1. Field of the Invention

The present invention relates generally to medical devices and methods. In particular, the present invention relates to an oral device that may be held in the mouth of a patient to reduce the incidence of obstructive sleep apnea or snoring.

Obstructive sleep apnea (OSA) is a serious medical condition resulting from a temporary airway blockage which occurs as a patient sleeps. The airway blockage usually occurs between the soft palate and/or the back of the tongue and the pharynx. As the patient breathes, the reduced area in the upper airway can cause snoring, and more seriously, OSA.

Sleep disruption caused by OSA can result in severe daytime sleepiness, chronic fatigue, headaches, depression, accidents, injuries, and of particular concern, OSA can reduce the amount of oxygen entering the lungs causing hypoxia. Hypoxia, in turn, can lead to pulmonary hypertension, heart disease, and stroke.

Numerous invasive and less invasive treatments have been proposed for OSA. Of particular interest to the present invention, “continuous positive airway pressure” (CPAP) delivers a continuous stream of pressurized air directly to the person\'s upper airway. The positive pressure maintains patency of the airway and inhibits the collapse associated with OSA. Although generally effective, CPAP suffers from a number of drawbacks that have led to a high level of non-compliance. The patient must wear a bulky facial mask which can be uncomfortable, and the system generates noise that can make falling asleep difficult. CPAP is also difficult to use because the mask requires careful fitting to avoid air leaks and facial discomfort and because the mask can easily be dislodged during sleep. Moreover, a number of unpleasant side effects, such as sore throats, dry throat and eyes, headaches, and skin rashes from the mask frequently occur. These problems have resulted in a high level of non-compliance with CPAP therapy.

As an improvement over CPAP, it has been proposed to apply a negative pressure to the forward end of the patient\'s mouth, typically at or just behind the lips, to pull the tongue forward in order to lift the rear portion of the tongue away from the back of the airway. See, for example, U.S. Patent Publication Nos. 2007/0277818, 2005/0166928 and 2005/0166929. While promising in theory, in practice it is very difficult to apply a vacuum in the region of the tip of the tongue to raise the base of the tongue and clear the patient\'s airway, particularly when the patient is lying on his or her back and gravity is pulling the tongue posteriorly. The tongue is a relatively large and compliant organ with significant mass, and applying a vacuum over a relatively small surface area at the tip will often not be effective in raising the back of the tongue against gravity. The moist and compliant tissues in the mouth are somewhat self-sealing, and this effect tends to inhibit the propagation of negative pressure, thereby confining the negative pressures to a relatively small area near the point of application. Thus, simply applying a vacuum at a location near the anterior tip of the tongue tends to draw the tongue up against the hard palate posterior to this location, creating a seal that restricts the propagation of vacuum through this region of contact toward the back of the oral cavity, where direct vacuum is usually required for maximum effectiveness.

As another improvement over CPAP, it has been proposed to place various devices in direct contact with the posterior tissues of the mouth such as the soft palate and posterior portions of the tongue. A major disadvantage of these approaches is that contact with certain tissues near the posterior area of the tongue may elicit the gag reflex and in any case the presence of such devices so far back in the mouth can be uncomfortable.

For these reasons, it would be desirable to provide alternative and improved methods and apparatus for treating obstructive sleep apnea and snoring. The methods and devices should be non-invasive and require no surgery or permanently implanted components. In addition, the methods and devices should be minimally intrusive with components that are comfortable and quiet so that disruption of the patient\'s sleep is minimized. Moreover, the methods and devices should avoid contacting the portions of the oral cavity that trigger the gag reflex. The methods and systems should also be simple to implement and be effective to significantly improve patency of a patient\'s airway during sleep. At least some of these objectives will be met by the inventions described hereinafter.

2. Description of the Background Art

Oral and external devices for treating sleep apnea and snoring are described in U.S. Patent Publication Nos. US2005/166929; US2005/166928; US2008/0188947; US2007/0277818; US2008/0216843; and US2008/0210244; and in U.S. Pat. Nos. 7,182,082; 7,073,506; 7,073,505; 6,955,172; 6,877,513; 6,494,209; 5,957,133; 5,465,734; 4,676,240; 4,304,227; 4,169,473; and 3,132,647; and in Cartwright and Samelson “The effects of a non-surgical treatment for obstructive sleep apnea: the tongue retaining device;” Journal of the American Medical Association 248 (1982).

The present invention provides methods and systems for improving airway patency in patients by creating a clear region or space above the tongue and applying a negative pressure within the clear region. The clear region creates an opening facing toward the soft palate upon which the negative pressure may act. The negative pressure acts to draw the soft palate away from the pharynx and usually to draw the rear portion of the tongue away from the pharynx as well. The clear region may also serve to create a space into which the soft palate may move while negative pressure continues to act on its free surface. In this way, the soft palate and posterior tongue are urged anteriorly without contacting tissues in a way that might elicit the gag reflex. By moving the soft palate and optionally the tongue in a forward or anterior direction, the patency of the airway behind the palate and tongue is enhanced to improve breathing. Usually, while the negative pressure is being applied, the patient\'s lips will be closed or sealed to inhibit the entry of air into the clear region. Additionally, application of the negative pressure will usually draw the soft palate into partial or complete contact with a surface of the rear tongue or with the device itself so as to create a seal which substantially fluidly isolates the airway from the clear region. In that way, the desired negative pressure may be maintained within the clear region with minimum air or fluid flow needed to maintain the negative pressure within the region. Because fluid flow is minimized this therapy can be very quiet and energy-efficient.

As used herein, “superior” refers to the direction toward the top of the oral cavity (or top of the head), “inferior” refers to the direction opposite the superior direction, “anterior” refers to the direction toward the front of the oral cavity or lips, and “posterior” refers to the direction toward the back of the oral cavity and airway, opposite the anterior direction. The terms “patency” and “airway” refer to the opening or clearing of the airway leading from the nasal cavity into the trachea located generally behind the soft palate and the rear of the tongue. To improve airway patency, the airway may be wholly or partially obstructed intermittently or temporarily for some time period over a normal sleep cycle, however, the airway will be open or partially open more than it would in the patient\'s untreated condition. The “upper portion of the soft palate” refers to the superior portion of the soft palate extending inferiorly from the end which connects to the hard palate to a point about ⅓-½ way toward the free inferior tip of the soft palate. The phrase “medial region” or “medial surface” of the tongue refers to a superior surface of the tongue which is spaced substantially posteriorly from the anterior tip of the patient\'s tongue and immediately anterior or forward of the region which initiates the gag reflex. While it may vary from patient to patient, the medial region will generally be the middle one third of the upper surface of the tongue which extends between the anterior tip of the tongue and the posterior end of the tongue (the posterior end being the location on the tongue that is furthest posterior in the oral cavity); i.e., the medial surface will usually include an area of the tongue that is at least about ⅓ of the way, more preferably at least about ½ of the way, from the anterior tip of the tongue to the posterior end of the tongue. Preferably, the medial region will include an area on the tongue posterior to the midpoint between the anterior and posterior ends of the hard palate. The phrase “clear region” refers to the space or volume above the tongue which will be cleared by the methods and devices of the present invention. The clearing will usually be achieved by engaging a surface against the superior surface of the tongue, typically using a member or element which engages the tongue and which is anchored within the oral cavity so as to constrain the tongue from raising into the clear region to interrupt the negative pressure which is being maintained. The term “vacuum” and the phrase “negative pressure” each refers to a total or partial vacuum which is maintained in the clear region, typically by controlled aspiration, where the pressure is maintained primarily in the range from 5 cm H₂O to 150 cm H₂O below the local atmospheric pressure. The “occlusal plane” is the plane in which the upper and lower teeth meet when the patient bites the upper and lower teeth together.

In a first specific aspect of the present invention, methods for improving airway patency in a patient comprise constraining a medial surface of the patient\'s tongue to maintain a clear region below the palate in an oral cavity. Negative pressure is applied within the clear region to open an airway behind the soft palate. Typically, the applied negative pressure closes a posterior portion of the soft palate against the tongue to draw the soft palate forward which in turn opens the airway behind the soft palate. By closing the soft palate against the tongue, the rear of the oral cavity is at least partially sealed so that the negative pressure applied within the clear region can be more easily maintained and can more readily draw both the soft palate tissue and the rear tongue tissue in a forward direction to help open the airway in the pharynx. The front of the oral cavity may also be at least partially sealed in order to inhibit air from entering the mouth. This may be facilitated by providing a sealing structure between the upper and lower lips and/or by providing a sealing structure between the lips and the teeth.

Constraining the medial surface of the patient\'s tongue may be accomplished in a variety of ways. Typically, a tongue constraint will be engaged against the medial surface to either depress the tongue or maintain the tongue in a lowered or depressed configuration (relative to the roof of the oral cavity) to provide the desired clear region below the palate and above the tongue. Typically, the constraint has a flat or an arch-like structure and may have a generally concave surface which engages the tongue. The tongue will typically be engaged at a point forward of a gag reflex response region, and the negative pressure is applied using a vacuum source positioned proximate the clear region, either within the clear region or adjacent to it. Typically, the vacuum source will have a plurality of ports or openings which permit a distributed aspiration of air and fluids from the clear region within the oral cavity. Often, multiple vacuum sources such as probes, portions of the tongue constraint, or portions of other structures described hereinafter, may be employed to again improve the distribution of the aspiration within the clear region. Usually, the distributed negative pressure or aspiration ports will be positioned within the clear region or adjacent rear portions of the oral cavity in order to assure that the desired negative pressure within the clear region is achieved. This is in contrast to prior art where the vacuum source may be positioned in a forward region of the oral cavity, typically behind the lips, generally in the region of the front teeth. Negative pressure or aspiration ports may also be positioned to apply negative pressure to other posterior portions of the mouth such as the sides of the tongue. Such ports may aid in urging portions of the tongue and soft palate forward by applying negative pressure into posterior oral spaces that can be at least partially sealed off by the compliant tissues of the mouth. It may be advantageous to apply different levels of negative pressure at various locations.

In preferred aspects of these methods for improving airway patency, remaining portions of the tongue will typically not be constrained, and the level of negative pressure applied within the clear region may be adjusted for comfort, to improve efficacy, or for other purposes. In addition, it may be desirable to deliver a fluid, such as water, humidified air, or the like, in order to moisten the oral cavity which might become dry after a prolonged exposure to aspiration. The fluid will typically be delivered during the application of negative pressure, but could also be delivered before, after, and at other times. In other instances, the mouth may be too moist, and fluid such as saliva or mucus will accumulate, in which cases it will be desirable to aspirate fluid which accumulates in the oral cavity, possibly through a separate negative pressure line. Aspiration of accumulated fluid will reduce the need for the patient to swallow during sleep and may be aided by delivery of additional fluid to the oral cavity such as air as described above.

In a second specific aspect of the present invention, methods for improving airway patency comprise positioning an anchor structure in a patient\'s oral cavity. The anchor structure typically carries or is otherwise coupled to a tongue constraint which engages a medial surface of the patient\'s tongue to maintain a clear region below the palate. A negative pressure is applied by a vacuum source which is positioned proximate the clear region of the oral cavity, where the negative pressure closes a posterior portion of the soft palate against the tongue to draw the soft palate forward. Often, the at least one vacuum source is coupled to or integral with the anchor structure so that the vacuum source is positioned proximate the clear region when the anchor structure is properly in place. Alternatively, the at least one vacuum source could be positioned separately from the anchor structure, in which case it will typically be formed as a separate probe or other assembly.

The anchor structure may comprise a bite structure which is held by the patient between the patient\'s teeth. Typically the bite structure will comprise at least one bite surface which is held between the teeth and a lip seal which helps seal the oral cavity when the bite structure is in the mouth. Alternatively, the bite structure may comprise upper and lower tooth-receiving channels which both receive the teeth and help seal the oral cavity when the bite structure is in the mouth. As an alternative to such bite structures, the anchor may comprise a hard palate engagement surface which is held in engagement against the hard palate (the roof of mouth) to hold the anchor in position to maintain the clear region.